Eco-building IV: Other renewable energies

As we continue to explore renewable energy sources, this issue we take a look at how wind and water power as well as geothermal energy and biomass can fuel a low CO2-emitting lifestyle. Next issue we will give you the tools you need to work these systems into your own home.

People have harnessed the wind’s energy for hundreds of years. Like old-fashioned windmills, today’s wind turbines use blades to collect the wind’s kinetic energy. Wind flows over the airfoil shaped blades causing lift, like the effect on airplane wings, causing them to turn. The blades are connected to a drive shaft that turns an electric generator to produce electricity. In 2005, wind farms increased ’s energy output by 27.3% in comparison to 2004, thus contributing 5.4% of the country’s overall gross electricity production.

Geothermal heat is found beneath the earth’s crust. New technologies allow it to be used directly for heating or tapped for electricity generation by channelling the steam to drive a turbine. By the end of 2007, global geothermal power capacity reached about 10 gigawatts. Geothermal can also be used for heat. There is evidence that high-temperature geothermal water was used to heat buildings in ancient Pompeii, the same type of energy currently heats most of ‘s buildings. The initial investment may seem costly but maintenance costs are minimal and it’s a great way to heat your home, swimming pool or domestic hot water.

Of the renewable energy sources that generate electricity, hydropower is the most often used. Directing, harnessing, or channelling moving water creates mechanical energy. The amount of available energy in moving water is determined by its flow or fall. Water flows through a pipe, or penstock, then pushes against and turns blades in a turbine to spin a generator to produce electricity. In a run-of-the-river system, the force of the current applies the needed pressure, while in a storage system, water is accumulated in reservoirs created by dams, then released when the demand for electricity is high. 24% of Spanish electricity comes from this source. Some regard hydropower as the ideal fuel for electricity generation because it is almost free, there are no waste products, and hydropower doesn’t pollute water or air. However, it is criticised because of its high impact on natural habitats. Industrial and developing countries alike, from to , are increasingly focusing their hydropower development on smaller-scale projects. Small-scale hydropower plants (up to 10 MW), if responsibly implemented, create relatively small social and environmental impacts, while providing people with power and related economic benefits. Globally, an estimated 73 gigawatts of small-scale hydropower capacity were installed by the end of 2006.

Biomass provides another ready source of energy. Agricultural wastes ranging from sugar cane to almond or olive residues can be burned directly or gasified and turned into electricity or combustible fuels. Power generation from biomass looks set to increase, and there are a number of biodiesel plants planned for Andalucía, as well as grants and incentives available to boost an ailing agricultural sector. Biomass-fuelled heating is also growing rapidly and now provides far more heat worldwide than solar and geothermal combined.

Biomass can also be used to produce biofuels, which continue to grow worldwide at a rate of 15-20 per cent. In 2006 the surge in production of the two most common biofuels, ethanol (derived mainly from sugar or starch crops), and biodiesel (made from vegetable oil or animal fats) accounted for 17 per cent of the increase in supply of all liquid fuels that year.

But with this rapid growth have come increasing concerns about the associated social and environmental impacts of biofuels. First-generation biofuels – particularly ethanol derived from corn and biodiesel made from palm oil – can cause significant environmental damage to soil and water quality, habitats and biodiversity. Over their lifecycle, biofuels can actually increase greenhouse gas emissions associated with the transport sector if, for example, corn ethanol is refined with energy from coal, or if palm oil plantations displace tropical forests in Southeast Asia. It is expected that second-generation fuels – that will rely primarily on organic wastes and algae – will have far lower environmental impacts. Depending on the selection of feedstocks and how they are grown and processed, who owns the farms and processing facilities, etc. biofuels could provide major environmental and social benefits. Thus, it is critical to speed the development and commercialisation of more sustainable advanced biofuels.

Renewable energies are set to become more and more prominent on the world stage in all their forms, and research and development will no doubt advance to keep up with demand. See next issue of La Chispa for how some of these can be developed at a domestic level.